Urban Sprawl: the Big Picture

October
11, 2002: While space technology was undergoing its
spectacular birth during the 1950s and '60s, and visionaries
were predicting the spread of human colonies into space, another
kind of human colony was spreading rapidly--right here on Earth!

It was the dawn of the modern suburb, a time of post-war prosperity
when housing developments popped up across the landscape like
mushrooms after a rain.

Right: A reconstruction of
the growth of Baltimore, Maryland, over the last 200 years. The
U.S. Geological Survey used historical records as well as Landsat
satellite data to create this sequence. Courtesy USGS.

A half-century later, we now understand that many environmental
problems accompany the outward spread of cities: fragmenting
and destroying wildlife habitat, for example, and discharging
polluted runoff water into streams and lakes.

The emerging space technology of the 1950s has grown along
with our cities. As you read this today, dozens of high-tech
satellites are circling our planet, gathering terabytes of scientific
data about the environment. These data provide a unique "big
picture" view of the effects of urban sprawl.

Unfortunately, many city planners still don't have access
to that big picture.

"Currently there's no good end-to-end system for getting
useful satellite data on the impacts of urban sprawl into the
hands of local decision makers," says Chet Arnold, associate
director of the Center for Land-use Education and Research at
the University of Connecticut (UConn). But he and his colleagues
at UConn are working with NASA to change that. They've started
a project called NAUTILUS to provide city planners satellite
data quickly and in a form that non-scientists can understand.

"NAUTILUS is one of seven Regional Earth Science Application
Centers (or "RESACs") around the country funded by
NASA," says Rodney McKellip, who manages the RESAC program
from the Stennis Space Center in Mississippi. Why NASA? The Earth
Science Enterprise of NASA is responsible for many of those satellites
circling the earth, and they are used to fulfill NASA's mission
to understand and protect our home planet. "RESAC
was started in 1998," continues McKellip, "as a way
to get vital Earth science information into the hands of local
and regional decision makers."

Currently,
the NAUTILUS team is developing their remote-sensing tools in
four test regions
in Connecticut, Massachusetts, Maine, and New Jersey. The local
public officials in these regions are making their information
needs known, and the scientists are learning to format the satellite
data in ways that meet those needs: color-coded maps, for example,
or time-lapse animations.

Left: During this
"NEMO" workshop in East Haddam, Connecticut, city
planning officials were shown how to understand and make use
of satellite data for land use decisions.

Because humans are so visually oriented, such graphics can
communicate lots of complex information in a quick, intuitive
way. Simply watching a 30-year animation that shows your city
rapidly engulfing the landscape can be an eye-opening experience.

"We all sat there a little stunned," says Christine
Nelson, recalling the first time she and her fellow city officials
were shown animations of historical city growth. Nelson, who
is the director of the land use department for the Town of Old
Saybrook, Connecticut, participated in a related UConn program
called Nonpoint Education for Municipal Officials (NEMO).

The satellite record gives a compelling view
of the past, but what about the future? After all, it's the future
consequences of land use that city planners must contemplate.

Right: This fictitious 3D
view of Hartford, Connecticut, is based on satellite and elevation
data [more
information]

One tool that the NAUTILUS researchers are using is like a
computerized "crystal ball." It's a software package
called CommunityViz
(based on the commercial map-viewing program ArcView) that lets
city planners envision a hypothetical future of their city, assuming
that it grew according to current zoning patterns. They can view
simple maps, color-coded for environmental impacts, or they can
choose to "fly through" a photorealistic 3D map of
their future city to get a more visceral sense of things to come.
More importantly, it lets them make changes and view the likely
outcome of different growth scenarios.

More-sophisticated techniques can wring all kinds of useful numbers
from satellite data: estimates of water-quality degradation due
to development, for example. Hard numbers like these are crucial
for making and justifying the tough decisions public officials
face.

In the cities involved with the NEMO and NAUTILUS pilot projects,
these accessible forms of satellite data have already had an
impact on decision making.

Nelson offers this anecdote from her own
Town of Old Saybrook: "Using these new satellite-based tools,
the planning commission recently realized that huge tracts of
unfragmented forest will be interlaced with paved roads as residential
development sprawls into the relatively undeveloped northwest
quarter of town."

Left: This aerial photo of a new housing development
shows how forest fragmentation begins. [more]

Such "forest fragmentation"
can cause problems. "Forest fragmentation occurs when large,
continuous forests are divided into smaller blocks, either by
roads, clearing for agriculture, urbanization, or other human
development," explains Arnold. "Increased fragmentation
due to urban development poses a threat to biodiversity primarily
in animal populations, as their habitats are chopped up (fragmented)
into smaller and smaller pieces."

To avoid these problems near the Town of Old Saybrook, "the
planning commission (inspired by the satellite data) is spearheading
modifications to the comprehensive plan of zoning regulations,"
notes Nelson.

Below: This NAUTILUS map
of Old Saybrook, Connecticut, is color-coded to show the percent
of the landscape covered by impervious surfaces (such as pavement
and rooftops) both today (left) and in the future (right) if
current zoning patterns are fully developed. Separate research
has shown that more than 25% of impervious surface (red) in an
area leads to major impairment of local waterways.

Bringing together the information for these maps also means
working out a lot of technical nitty-gritty. There are dozens
of Earth-observing satellites: Terra, Aqua, Landsat,
SPOT and IKONOS, for example. Each carries its own suite
of scientific instruments. Which
data should the NAUTILUS system use? And how can the 30-year
satellite record--taken from a series of satellites with different
properties--be integrated into a consistent record of changes
in the landscape during that time?

The NAUTILUS program is working these details out so that
city planners don't have to. If the project is successful, other
cities will soon join Old Saybrook in using satellites to better
understand the environmental impact of humanity's expanding "colonies"
here on Earth.

NAUTILUS -- short for "Northeast
Application of Useable Technology In Land planning for Urban
Sprawl," NAUTILUS is the project featured in this story.
See also the The Center for Land use Education And Research (CLEAR) and Nonpoint Education
for Municipal Officials (NEMO)

Right: Click on the image to view
more visualizations of urban sprawl and forest fragmentation.
[more]